u-0126 and icaritin

N-methyl-D-aspartate (NMDA) receptors are key signaling molecules that mediate excitotoxicity during cerebral ischemia. GluN2A-containing NMDA receptors, which are mostly located in the intrasynaptic region, mediate normal physiological processes and promote neuronal survival. GluN2B-containing NMDA receptors, which are mostly located in the extrasynaptic region, mediate excitotoxicity injury and promote neuronal death during ischemia. This study investigated the ability of icaritin (ICT) to protect against cerebral ischemia‒reperfusion injury (CI/RI) by regulating GluN2B-containing NMDA receptors through extracellular signaling regulatory kinases/death associated protein kinase 1 (ERK/DAPK1) signaling. A rat CI/RI model was established by transient middle cerebral artery occlusion (tMCAO). Following treatment with ICT and the ERK-specific inhibitor U0126, cerebral infarction, neurological function, and excitotoxicity-related molecule expression were assessed 24 h after reperfusion. ICT treatment significantly decreased cerebral infarct volume, improved neurological function, and regulated NMDA receptor subtype expression and ERK/DAPK1 signaling activation. The ability of ICT to increase GluN2A and postsynaptic density protein 95 (PSD95) mRNA and protein expression, inhibit GluN2B expression, and regulate DAPK1 activation was reversed after administration of the ERK-specific inhibitor U0126. These data indicated that ICT inhibited excitotoxicity injury and exerted a protective effect against CI/RI that was likely mediated by increased ERK signaling pathway activation and regulation of extrasynaptic and intrasynaptic NMDA receptor function, providing a new therapeutic target for ischemic encephalopathy.

Topics: Animals; Brain Ischemia; Neurons; Rats; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; Signal Transduction

The mechanism for icaritin to improve postmenopausal osteoporosis (PMOP) has not been clarified. The aim of this study was to investigate the role of estrogen receptor α36 (ERα36) in the proliferation promotion and anti-apoptosis effects of icaritin on osteoblasts and the underlying mechanism of downstream signal transduction. The ERα36 knockdown human osteosarcoma MG63 cell model was constructed by transfection of shRNA vector. Cell proliferation was detected by CCK-8, the apoptosis was detected by flow cytometry, and the activation of ERK and AKT signaling pathways was detected by Western blot. The results showed that the effects of icaritin on the proliferation and apoptosis of MG63 cells were significantly decreased after ERα36 knockdown, and icaritin could up-regulate the levels of ERK and AKT phosphorylation in MG63 cells, which could be reduced by ERα36 knockdown. The effect of icaritin on the proliferation of MG63 cells was significantly decreased by pretreating the cells with U0126 (an ERK signaling pathway blocker) and LY294002 (an AKT signaling pathway blocker), respectively. Furthermore, anti-apoptotic effect of icaritin on MG63 cells was significantly decreased after the cells were pretreated with U0126, but not with LY294002. These results suggest that icaritin exerts proliferation promotion and anti-apoptosis effects on osteoblasts through ERα36 and its downstream ERK and AKT signaling pathways.

Topics: Apoptosis; Butadienes; Cell Line, Tumor; Cell Proliferation; Chromones; Flavonoids; Humans; Morpholines; Nitriles; Osteosarcoma; Phosphorylation; Receptors, Estrogen; Signal Transduction; Up-Regulation